In a typical cellular system, also referred to as a wireless communications network, wireless terminals, also known as mobile stations and/or user equipment units communicate via a Radio Access Network (RAN) to one or more core networks. The wireless terminals can be Machine-to-Machine (M2M) devices, Internet-of-Things devices, mobile stations or user equipment units such as mobile telephones also known as “cellular” telephones, and laptops with wireless capability, for example, portable, pocket, hand-held, computer-comprised, or car-mounted mobile devices which communicate voice and/or data with radio access network.
The radio access network covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g., a Radio Base Station (RBS), which in some networks is also called “NodeB” or “B node” or “Evolved NodeB” or “eNodeB” or “eNB” and which in this document also is referred to as a base station. A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. The base stations communicate over the air interface operating on radio frequencies with the user equipment units within range of the base stations.
In some versions of the radio access network, several base stations are typically connected, e.g., by landlines or microwave, to a Radio Network Controller (RNC). The radio network controller, also sometimes termed a Base Station Controller (BSC), supervises and coordinates various activities of the plural base stations connected thereto. The radio network controllers are typically connected to one or more core networks.
The Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the Global System for Mobile Communications (GSM), and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for user equipment units (UEs). The Third Generation Partnership Project (3GPP) has undertaken to evolve further the UTRAN and GSM based radio access network technologies. Long Term Evolution (LTE) together with Evolved Packet Core (EPC) is the newest addition to the 3GPP family.
An example of a node in the core network is a mobility management node. Examples of a mobility management node are a Serving General Packet Radio Service Support Node (SGSN), a S4-SGSN and a Mobility Management Entity (MME). Such nodes are responsible, for example, for idle mode UE tracking and paging procedures including retransmissions. Mobility management nodes are also involved in bearer activation/deactivation and handover procedures. Mobility management nodes may be stateful or stateless. It is preferred that a stateful mobility management node serves the wireless device based on wireless device context information stored in the mobility management node itself. It is preferred that a stateless mobility management node serves the wireless device based on wireless device context information stored outside the mobility management node in a database that is used only by the specific mobility management node itself. Wireless device context information may e.g. include session states of the wireless device, e.g. such as values or flags or similar being set based one or more preceding events or similar relating to the wireless device. In addition, both stateful and stateless mobility management nodes may serve the wireless device based on other information than the wireless device context information, e.g. such as input parameters supplied to the mobility management for serving the wireless device.
In a stateless architecture, a mobility management node will save the wireless device context information, for example, UE context or similar, in an external database. For a migrating network, stateless mobility management nodes will exist together with legacy stateful mobility management nodes with an internal database holding the UE context. Some cells in the network may be served by legacy nodes while some cells may be served by parts of the core network which are upgraded to a virtualized implementation where states are saved in an external database.